A rotary separator may be used to separate substances having relatively high densities, such as liquids, from a pressurized flow stream, such as a natural gas flow stream. During the operation of a typical rotary separator, a vortical flow is developed in the process stream as it flows through a rotating drum. The fluid is subject to an inertial acceleration field, resulting in centrifugal forces directed radially outward towards the inner surface of the drum. The substances having relatively high densities in the vortical flow stream, such as liquids, are subject to the highest centrifugal forces. Thus, liquids present in the flow stream are centrifuged and captured against the inner surface of the drum, thereby radially separating the liquids (high-density substances) from the gas (low-density substances). As a result, a “clean” or substantially non-liquid-transporting gas flow stream exits axially from the drum and flows downstream of the rotary separator.
However, several problems may arise during the operation of a typical rotary separator. For example, a self-powered rotary separator, that is, a rotary separator in which the rotating drum is powered by the process flow stream, may have a limited liquid-handling capacity, and an appreciable amount of liquid in the flow stream may decrease the separation efficiency.
Another problem arises in connection with variations in the volumetric flow rate of the pressurized flow stream. Operation of a typical rotary separator at an off-design volumetric flow rate may result in either a decrease in the separation efficiency of the separator (in the case of a decreasing flow rate), or an increase in the pressure drop across the separator (in the case of an increasing flow rate).
Other operational problems include a decrease in the separation efficiency of the separator because of decreases in fluid velocities within the drum due to any static surfaces about which the drum rotates. Also, the rate of liquid drainage from the separator may be not be sufficient relative to the rate of separation of the liquid from the gas, possibly causing liquid to back up in the separator. Further, any changes in pressure in the flow stream may fatigue various components in the separator, such as bearing assemblies. Also, due to flow resistances associated with the rotating drum, a secondary flow stream of gas may be driven around the outside of the drum. Since the secondary flow stream has not undergone rotary separation in the drum, it may transport liquid which then may be reintroduced into the gas flow stream downstream of the drum. Thus, re-contaminated gas (or liquid-carrying gas) may be transported downstream of the separator, frustrating the purpose of the separator.
Therefore, what is needed is a separator and/or method that overcomes one or more of the above-described problems, among others.